Method and circuit for correcting sensor temperature dependency characteristic

Abstract

A method and circuit for preventing an output signal, which has been corrected through digital correction or analog correction, from deviating from a target value and for preventing power supply noise and power consumption from increasing. A sensor amplification circuit receives output of a sensor as an input signal. Correction points are set at predetermined temperature intervals. The sensor amplification circuit performs digital correction for correcting the input signal with correction data set for each correction point. Further, the sensor amplification circuit performs a second correction for correcting the input signal between the correction points with gradient data calculated from the correction data for two of the correction points that are adjacent to each other.

1. A method for correcting an input signal having a temperature dependent characteristic, the method comprising:
 setting correction data for each of a plurality of correction points set at a predetermined temperature interval; 
 generating an output signal having a predetermined characteristic curve by amplifying the input signal; 
 performing a first correction for correcting the input signal with the correction data to change the characteristic curve of the output signal; 
 calculating gradient data between two of the correction points that are adjacent to each other from the correction data for each of the two adjacent correction points; and 
 performing a second correction for correcting the input signal with the gradient data to change the characteristic curve of the output signal. 
 
     
     
       2. The method according to  claim 1 , wherein said setting the correction data includes changing the predetermined temperature interval between the two adjacent correction points in accordance with the temperature dependency characteristic of the input signal. 
     
     
       3. The method according to  claim 1 , further comprising:
 comparing the correction data for a given correction point with the correction data for at least one of two correction points adjacent to the given correction point; 
 repeating said comparing for each correction point; and 
 determining whether the first correction or the second correction is necessary based on the comparison. 
 
     
     
       4. The method according to  claim 1 , further comprising:
 comparing the correction data for each of the correction points with the correction data for each of two correction points adjacent to that correction point and determining whether the first correction or the second correction is necessary for each correction point based on the comparison; and 
 performing the first correction or the second correction based on the determination. 
 
     
     
       5. The method according to  claim 1 ,
 wherein said performing a first correction includes changing the characteristic curve of the output signal by correcting the input signal based on the correction data so that the characteristic curve converges to a predetermined target value regardless of temperature; and 
 wherein said performing a second correction includes changing the characteristic curve of the output signal by correcting the input signal based on the gradient data so that the characteristic curve converges to a predetermined target value regardless of temperature. 
 
     
     
       6. A correction circuit for correcting an input signal having a temperature dependent characteristic, the correction circuit comprising:
 a memory device for storing correction data for each of a plurality of correction points set at a predetermined temperature interval; 
 a first correction circuit for correcting the input signal at each correction point based on the correction data corresponding to each correction point; 
 a second correction circuit for correcting the input signal between two of the correction points that are adjacent to each other based on gradient data calculated from the correction data for each of the two adjacent correction points; 
 a sensor for detecting temperature; 
 a control circuit for reading the correction data corresponding to the temperature detected by the temperature sensor from the memory device and controlling operation of the first correction circuit and the second correction circuit based on the correction data; and 
 an amplification circuit unit, including the first correction circuit and the second correction circuit, for correcting the input signal with the first correction circuit and the second correction circuit to generate an output signal having a predetermined characteristic curve. 
 
     
     
       7. The correction circuit according to  claim 6 , wherein the predetermined temperature interval between the two adjacent correction points is changed in accordance with the temperature dependency characteristic of the input signal. 
     
     
       8. The correction circuit according to  claim 6 , wherein the control circuit includes:
 a determination unit for comparing the correction data for a given correction point with the correction data for at least one of two correction points adjacent to the given correction point and for determining whether correction with the first correction circuit or the second correction circuit is necessary based on the comparison, wherein the determination unit repeats said comparing for each correction point. 
 
     
     
       9. The correction circuit according to  claim 6 , further comprising:
 a determination unit for comparing the correction data for each of the correction points with the correction data for each of two correction points adjacent to that correction point, determining whether correction with the first correction circuit or the second correction circuit is necessary for each correction point based on the comparison, and storing the determination in the memory device; and 
 wherein the control circuit controls operation of the first correction circuit and second correction circuit based on the determination. 
 
     
     
       10. The correction circuit according to  claim 6 ,
 wherein the first correction circuit adjusts gain and offset voltage of the amplification circuit unit based on the correction data so that the characteristic curve of the output signal converges to a predetermined target value regardless of the temperature; and 
 wherein the second correction circuit adjusts the gain and the offset voltage of the amplification circuit unit based on the gradient data so that the characteristic curve of the output signal converges to a predetermined target value regardless of the temperature. 
 
     
     
       11. The correction circuit according to  claim 6 , wherein the correction circuit is connected to a sensor and receives an output signal of the sensor as the input signal.